fix(plan): readable audit descriptions, project labels, dashboard invalidation, view-only & sticky-column UI

Work-plan fixes from this session:
- Czech audit descriptions for plan entries/overrides (was empty '-')
- server-embedded project label on grid cells (was '-' past the 100-project cap)
- dashboard activity + audit-log cache invalidation on plan mutations
- read-only cells: no '+' on empty, keep hover on cells with a record
- view modal: Czech category + formatted dates
- sticky date column made opaque (no bleed-through on horizontal scroll)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/lib/queries/plan.ts

@@ -18,12 +18,52 @@ export interface ResolvedCell {
   user_id: number;
   shift_date: string;
   project_id: number | null;
+  /** Project label resolved server-side (see resolveGrid). Lets the UI show
+   * the project without depending on the capped/permission-gated projects
+   * list. Null when the cell has no project. */
+  project_number: string | null;
+  project_name: string | null;
   category: string;
   note: string;
   rangeFrom: string | null;
   rangeTo: string | null;
 }
 
+/** Czech labels for the plan_category enum — single source of truth shared
+ * by the grid chips, the detail view, and aria-labels. */
+export const PLAN_CATEGORIES: ReadonlyArray<{ value: string; label: string }> =
+  [
+    { value: "work", label: "Práce" },
+    { value: "preparation", label: "Příprava" },
+    { value: "travel", label: "Cesta / Montáž" },
+    { value: "leave", label: "Dovolená" },
+    { value: "sick", label: "Nemoc" },
+    { value: "training", label: "Školení" },
+    { value: "other", label: "Jiné" },
+  ];
+
+const PLAN_CATEGORY_LABELS: Record<string, string> = Object.fromEntries(
+  PLAN_CATEGORIES.map((c) => [c.value, c.label]),
+);
+
+/** Czech label for a plan category, falling back to the raw value. */
+export function planCategoryLabel(value: string): string {
+  return PLAN_CATEGORY_LABELS[value] ?? value;
+}
+
+/** Build the display label for a cell's project, preferring the server-
+ * embedded fields. Returns null when the cell has no project. */
+export function cellProjectLabel(cell: {
+  project_number: string | null;
+  project_name: string | null;
+}): string | null {
+  if (!cell.project_number && !cell.project_name) return null;
+  if (cell.project_number && cell.project_name) {
+    return `${cell.project_number} — ${cell.project_name}`;
+  }
+  return cell.project_number ?? cell.project_name;
+}
+
 export interface GridData {
   view: "week" | "month";
   date_from: string;